The turnout at the recent industry seminar at Vollmer UK underlined industry concern to keep pace with the fast changing world of tool and sawblade technology.
The October event, run at Vollmer’s Nottingham headquarters in association with CNC grinding machine specialist ANCA UK, attracted 100 delegates from the tool supply and service sector and was addressed by highly qualified speakers from industry, consultancy and academia.
The first speakers at the seminar, entitled “Manufacturing and resharpening of tools and sawblades in the woodworking, sawmill and engineering industries”, looked at modern machining requirements. Anthony Deeming of metalworking tooling manufacturer Hydra Clarkson International focused on the rapid development of high-speed machining (HSM) over the past five years. HSM increases quality and productivity while reducing costs, but puts many constraints on the design of tools.
Mark Smith of SCM Group UK told delegates that current and future requirements in the woodworking sector are for machines that feature simple operation and rapid changeovers, as well as higher feed speeds on medium batch runs and a high quality finish.
Traditional methods
The traditional way of achieving this is to use a ‘jointed’ machine with mechanical handling. However, this requires a large investment, with special and expensive tooling and techniques, and changeovers are slow.
SCM’s answer has been to develop machines with high speed spindles. At 7,000rpm there is a 15% increase in feed speed compared with 6,000rpm, rising to 38% at 8,300rpm and 100% at 12,000rpm. Higher spindle speeds give rise to tooling problems, including noise when cutting and idling, the body weight of the tool, and increased power requirements.
Developments in technology for manufacturing and resharpening tooling to meet these modern demands were presented by Vollmer UK’s sales director Graham Hopkins, who reviewed the com-pany’s range of machinery for wide bandsaw blades, TCT circular sawblades and PCD-tipped sawblades and tooling.
Key areas of development include advanced CNC systems for greater flexibility and precision, automated robot-loading of the machines and the use of integral measuring probes.
Another important feature is the widespread use of wet-grinding technology, with fully enclosed machines throughout Vollmer’s range. This improves operator safety and the working environment as well as contributing to a higher quality finish of the tool.
Martyn Cross of ANCA UK presented an overview of his company and its CNC machines for metal-working – including tool and cutter grinders, punch grinders and special machines developed for specific industry requirements.
Machinery from Vollmer and ANCA was available for demonstration during the seminar.
Tom Pearce of the Institute of Grinding Technology (IGT) highlighted some recent areas of research. IGT runs training courses and publishes the Grinding Manual as well as offering wide-ranging consultancy services – including visiting manufacturers’ factories to identify problems and suggest solutions.
One test that is becoming more popular is for acoustic emission, since this can help determine the amount that has to be dressed from expensive CBN grinding wheels in order to achieve optimum grinding results.
David Balshaw of Saint Gobain Abrasives explained the importance of choosing the correct grinding wheel. Wheels with a less wear resistant or softer bond will save some time but produce a rougher surface and more wheels will be needed; those with a more wear-resistant or harder bond will take more time, require good cooling, damage the cutting edge and require stiffer tool holding, but fewer wheels will have to be bought.
A balance is therefore required – a wheel that is not too hard and not too soft, using bonds and grits suited to the component materials. Ensuring good wheel specifications – as well as optimum speeds, feeds and removal rates – would result in the lowest grinding costs and higher performing cutting tools.
Grinding fluid technology was covered by Geoff Hornsby of GSK Services. Fluids fall into two basic categories: water-based (synthetics, semi-synthetics, micro-emulsions, emulsions and high oil emulsions); and oil-based (mineral oils, hydrocracked oil, esters and synthetic neat oils).
Increased life
Their desired effect is to increase material removal rate, increase grinding wheel life, increase ground component quality, prevent corrosion and remove heat and grinding fines. Selecting the correct product for a particular application requires many factors to be considered. Grinding performance also depends on correct machine set-up (filtration, delivery pressure, nozzle geometry, sufficient volume of fluid, temperature control) – and it is essential to have effective maintenance programmes in place.
Peter Stokley of Balzers offered a fascinating insight into tool coating technology. There are two main categories of coatings – PVD (physical vapour deposition), which requires temperatures in the region of 500OC; and CVD (chemical vapour deposition), where temperatures of 850-1,100OC are needed.
In the past five years there has been a huge increase in the use of carbide inserts, 80% of which are coated. If carbide is heated to temperatures of 1,000OC or more the corners round off, whereas PVD technology retains the sharp contour.
Developments in coatings have gone hand-in-hand with developments in machinery and materials. The past 25 years have seen progress from multi-purpose coatings to those developed for specific applications – delivering huge increases in tool life and cutting performance.
The final two sessions of the seminar looked at polycrystalline diamond (PCD). First, Neels Pretorious of PCD manufacturer Element 6 (formerly De Beers Industrial Diamond Division) described the production process for the PCD segments that are brazed onto tooling to form the cutting edge.
PCD-tipped tooling is used for abrasive wood products (chipboard, fibreboards and particleboards as well as hardwoods), non-ferrous metals, hard metals and ceramics, and polymers. A survey by Element 6 in 2000 showed that the largest segments of the global woodworking market for PCD-tipped tools were coated chipboard (27%) and laminate flooring (14%).
Trends that are expected to drive further growth in demand for PCD-tipped tools include increased use of composites and wood-based materials – coupled with the need for better production quality and efficiency and environmental factors (noise reduction and lower energy consumption).
David Aspinwall of the University of Birmingham heads leading research into electrical discharge machining (EDM) of PCD. EDM removes material by melting and vapourisation, as a result of electrical discharges between the machine’s electrode and the workpiece, with the gap between the two flooded with dielectric fluid.
EDM is used for more than 50% of tools manufactured with PCD. Complex tool shapes are possible, which is especially relevant in the woodworking industry, and because it is a non-contact process there are negligible forces to affect tool shape and fixturing.
With the presentations completed, delegates were invited to join Vollmer at a seminar dinner in a nearby hotel. The ‘social’ side of Vollmer’s industry events brings real benefits by allowing colleagues from the tooling supply and servicing sector to meet and discuss mutual concerns.
